US2471031A

US2471031A - Hydraulic transmission

Info

Publication number: US2471031A
Application number: US554821A
Authority: US
Inventors: Vernon E Gleasman
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-09-19
Filing date: 1944-09-19
Publication date: 1949-05-24
Anticipated expiration: 1966-05-24

Description

May 24, 1949. v. E. GL EASMAN HYDRAULIC TRANSMISSION 7 Filed Sept. 19, 1944 4 Sheets-She et 1 W MS a 6 M M m May 24, 1949. i v. E. GLEASMAN 4 Sheets-Sheet 2 Filed Sept. 19, 1944 May 24, 1949.- v. E. GLEASMAN HYDRAULIC TRANSMISSION 4 Sheets-Sheet 3 Filed Sept. 19, 1944 KER/V0 E. GZEASMAA/ v. E. GLEASMAN 2,471,031

HYDRAULIC TRANSMISSION 4 Sheets-Sheet 4 May.24, 1949.

Filed se t; 19, 1944 VERA/0N E 62 [A SII/NV Patented May 24, 1949 UNITED STATES PATENT oi-"FlcE HYDRAULIC TRANSMISSION Vernon E. Gleasmam Elmlra, N. Y. Application September 19, 1944, Serial No. 554,821

This invention relates to a hydraulic transmission and has as an object to provide a-transmission having an improved arrangement of rotary pumps mounted in a housing or casing carried by a drive shaft and having geared connection with a driven shaft, the gears of the pumps and the driven shaft being located within the casing and so arranged that the pump gears may turn the driven shaft at the same speed as the driving shaft, or turn about the gear of the driven shaft to cause rotation of the driven shaft at a reduced speed.

Another object is to so form the pumps that as they rotate, oil or an equivalent liquid will be circulated through the casing, the freedom of circulation controlling ratio of rotation between gears of the pumps and the gear of the driven shaft with which they mesh and consequently the speed ratio between the drive shaft and the driven shaft.

Another object is to provide an improved valve having a collar slidable along the drive shaft and carrying valve plungers passing through openings in the transmission casing and movable'into and out of position to fully or partially cut off flow of liquid through'outlets of" the pump chambers.

Another object of the invention is to so form the valve and liquid outlets of the pump chambers that one plunger may control flow of liquid from a plurality of pump chambers.

Another object of the invention is to so arrange fluid passages of the transmission casing that during rotation of the drive shaft and the casing, centrifugal force created by such rotation will tend to move liquid toward the periphery of the casing and thus cause liquid to very readily enter inlets of the pump chambers.

Another object of the invention is to provide a transmission of such construction that speed of rotation imparted to the driven shaft may be progressively increased or decreased very gradually.

In the accompanying drawings:

Fig. 1 is a vertical sectional view taken through the transmission longitudinally thereof.

Fig. 2 is a transverse sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a sectional view on the line 3-3 of Fig. 1.

Fig. 4 is a fragmentary sectional view taken Fig. 5 is a sectional view on the line 5-5 of 17 Claims. (Cl. 74-774) Fig. 6 is a fragmentary sectional view showing the construction of the valve for controlling speed at which the driven shaft rotates.

Fig. 6A is a view similar to Fig. 6 showing the valve opened.

Fig. 7 is a sectional view taken longitudinally through a transmission of modified construction.

Fig. 8 is a sectional view taken on the line 8-8 of Fig. 7.

Fig. 9 is a fragmentary sectional view taken through one of the pumps longitudinally thereof.

This improved hydraulic transmission has a casing l formed of strong metal and circular in cross section, as shown in Fig. 2. The end wall 2 of the casing or housing I is formed integral therewith but the other "end of the casing is formed open to receive a block 3 which fits snugly within the casing and about its periphery is formed with a flange 4 having openings 5 therein. These openings register with threaded sockets 6 so that screws I may be passed through openings 5 and screwed tightly into the sockets 6 to firmly but removably hold the block 3 in p ace.

The block 3 carries a drive shaft 8 which is shown integral with the block but may be suitably fixed at the center of the outer side face thereof, and the inner side face of the block is spaced from the wall 2 in order to provide a chamber 9 within the casing. At its inner side the block I is formed with a centrally located socket ill to rotatablyireceive the reduced inner end portion ll of a driven'shai't 12. A thrust hearing I; is mountedat the center of the socket and the inner end of the driven shaft and there has also been provided a bushing I4 which fits snugly within the socket and also passes through an opening II formed'jcentrally of the face plate It of the block and registering with the socket Ill. The chamber Iis filled with oil, or other suitable liquid, through an opening ll which is then closed by a threaded plug screwed into the fillin opening and, inorder to prevent leakage of oil out of the chamber" about the driven shaft, there has been provided a packing box l8 of conventional formation. A gear is (Fig. 3) is keyed to the driven shaft'li within the chamber 9 and meshes with-gears 20 keyed to shafts 2| which have their outer'ends rotatably mounted in sockets 22 formed in the inner surface of the wall 2 and evenly spaced from each other circumferentially thereof; The shafts 2| constitute pump shafts and pass through openings 23 formed in the face plate It and through pump chambers 24, with their inner ends rotatably mounted in sockets formed centrally of inner ends of the pump chambers. Necks 28 project forwardly from the face plate It about the openings 23 and carry packing glands or nuts 26' to prevent escape of oil from the pump chambers 24 about the pump shafts 2|.

The pump chambers 24 are of duplicate formation and each has its side wall concentric to the shaft 2| for a portion of its circumference and for the remainder of its circumference, eccentric to the shaft, as shown in Figs.'2 and 4, so that, as the shaft rotates, blades 21 carried by the shaft and extending radially thereof, may have compressing action upon oil in the offset portion of the chamber. The blades are slidably mounted on grooves or seats 21' formed in the shaft and are urged outwardly by springs 28 which keep the outer ends of the blades pressed firmly against the side wall of the pump chambers 24. The oil enters the pump chambers through inlets 29 near the periphery of the block 3 and, as the blades move through the offset portions of the chambers, the oil is forced under pressure through outlets 30 and into a circular channel 3| from which it flows through passages 31 in wall i8 back into the chamber 9. When the oil is allowed to flow freely through the groove 3| and the passages 31, the pump shafts and their blades may move freely in the pump chambers and the gears 20 will travel about the gear 19 without turning the gear l9 and the driven shaft. When flow of oil through groove 3! and passages 31 is cut off, the pressure created by action of the pump blades will prevent turning of the pump shafts and, since the gears 20 will then be prevented from traveling about the gear [9, the driven shaft i2 will turn at the same speed as the drive shaft 8. By partially cutting of! flow of oil from the pump chambers, rotation of the pump shafts may be reduced and, as the pump shafts turn, the gear ill will be turned with them at a slower rate of speed than the speed at which the drive shaft turns. Therefore, by gradually cutting off flow of oil from the pump chambers, the speed at which the driven shaft rotates may be gradually reduced from full speed to a full stop.

' The valve by which flow of oil from the pump chambers is controlled consists of a collar 38 which fits about the drive shaft 8 and is slidable therealong, the collar being provided with plungers 39 slidably received in openings 40 formed through the block 3 longitudinally thereof and alined with the outlets 21. The openings 40 intersect the groove 3| and when the plungers are in the position of Fig. .6, flow of oil through outlets 31 will be cut off. The plungers are formed with circumferentially extending grooves 4|, and, from an inspection of Fig. 6, it will be seen that any oil attempting to flow along the plungers will upon reaching groove 4|, flow back through drawing openings 40A. By sliding the collar 38 along the drive shaft, the plungers will be shifted longitudinally and their inner ends moved into or out of the outlets 31 and the groove 3|. When the plungers 39 are in position to extend across the groove ii and enter theports 31, the ports are closed and fluid under pressure that might escape along plungers 40 would be trapped and brought back to the reservoir through the passage 40A. These passages 40A are drilled at an angle so that centrifugal force will act to remove any fluid that might enter the passage.

By arranging the oil passages as shown in Fig. 2, a pair of plungers may control flow of oil from .4 four pumps in an infinite manner between zero and 100%. This arrangement also disposes two pumps on each side of each valve plunger and maintains a hydraulic balance on the valve plungers so that they will actuate freely under pressure. The pump shafts are each formed with a longitudinally extending bore 42 which communicate with the grooves 21 and have branch ports 43 communicating with the chamber 9, so that, during operation of the transmission, air or oil may flow into and out of inner ends of the grooves 21 and thus. prevent formation of fluid cushions which would interfere with proper sliding of the blades 21.

In Fig. 7, there has been shown a transmission of modified construction. In this embodiment, the front wall 44 of the casing 45 is formed at its center with an extension 46 carrying an adaptor 41 at its outer end. The driven shaft 48 is rotatably mounted through the extension 46 andthe adapter 41, and the extension is formed with circumferentially spaced oil passages 49 so that oil in the chamber 50 of the casing may flow through these passages into a chamber 5i and into the pocket 52 of the adaptor 41, from which the oil flows through a pipe 53 to an oil reservoir 53A.

Packings

54 and 55 are provided at ends of the adaptor to prevent leakage and allow the casing to turn, while the adapter 41 remains stationary.

The block 56, which fits snugly within the rear portion of the casing 45 and is secured thereto so that the casing turns with the drive shaft 51 projecting rearwardly from the casing, is formed with pump chambers 58 closed at their front nds by face plate 59. A socket 60 is formed at the center of the block 56 to rotatably receive the inner end portion of the driven shaft 48, so that the casing 45 and block 58 may turn about the driven shaft when the driven shaft is to be turned at a speed slower than the speed of the drive shaft. Pump shafts 8| extend through the chamber 50 in spaced parallel relation to the driven shaft with their front ends rotatably mounted in sockets 62 formed in the wall 44. These pump shafts 6i are rotatably mounted through bearing sleeves 63 having packings 64 at their front ends, and the shafts carry gears 65 which mesh with the the gear 86 carried by the driven shaft. When the pump shafts are held against rotation in the sleeves and sockets, the gears 65 may not travel about the gear 66 and the driven shaft turns at the same speed as the drive shaft. When the gears 65 are permitted to travel about the gear 66, the driven shaft 48 will be rotated at reduced speed, or it will remain stationary, according to the freedom with which the gears are permitted to travel about the gear 66. The pumps 61 from which the pump shafts extend are rotatably received in the pump chambers 58 and carry blades 68 which are urged outwardly by springs 69 coiled about pins 69', so that, as the pumps rotate, the blades will be maintained in contact with the peripheral walls of the pump chambers. The pump chambers each has its peripheral wall formed with a portion eccentric to the pump operating therein and with this portion communicates an inlet port 10, the ports being extending laterally from outer ends of passages 'll formed in the block radially thereof and leading from an inlet passage 12 extending longitudinally of the drive shaft. The outer end of the inlet passage communicates with a feed pipe 13 leading from the reservoir 53A to which pipe 58 extends and a coupling 14 connects the feed pipe the outlets of the block and into the chamber 50, from which the oil flows through the extension 46 and through pipe 53 back to the reservoir.

When fiow of oil from the pump chambers is unrestricted, the'pump shafts turn freely and their gears 65 move about the gear 68 without causing rotation of the. driven shaftbut, by obstructing flow of oil from the pump chambers, the pressure created will retard or entirely pre vent turning of the pump shafts and rotary motion will be imparted to the driven shaft. The

speed at which the driven shaft rotates depends upon the extent to which movement; of the gears: 65 about gear 68 is retarded,- and it is to be understood that this may be gradually effected-until rotation of the pump shafts and their gears is entirely stopped and the driven shaft caused tov turn at the same speed as the drive shaft. The valve by which flow of oil from the pump chambers is regulated has a collar 16 which is slidable along the drive shaft and plungers 11 carried by the collar and passing through openings in the block with their inner portions adapted 'to gradually move into or out of blocklng relation to the outlets of the pump chambers, accord n to the direction in which theblockfl drive shaft. This valvefmech hasjnot been illustrated in 'detail' as it isbf the same construe? ticn previously shown and describeda 1' 5 n s The fiuid pumps are used tofretardrotatlon 3f the shafts. Therefore, they may be termed"!!- fiuid brakes. It should also be'noted that these -umps arev designed for minimum volume and :iaximum power, instead of maximum volume nd minimum power, since they; are to serve as, "rakes and notmerely as pumps; :1" j

Having thus described the inventiom-what is claimed is: I

1. In a hydraulic transmission, a casing open at one side, a block closing the open side of said casing and spaced.from the opposite side thereof to provide achamber in the casing for containing liquid, a rotary drive shaft extending outwardly from said block, a driven shaft passing through the center of the second side of the casing into said chamber and rotatably mountedin a bearing at the center of; said blockfs aid block being formed with pump chambers spaced-from each other circumferentially thereof,.:;rotary pumps operating in said pumpchambers and having shafts extending into the liquid chamber in spaced parallel relation to the driven shaft, a gear car- I ried by the driven shaft within the liquid chamber, gears carried by the pump shafts and meshing with the gear of the driven shaft, the pump chambers each having an inlet adjacent the periphery of the block and an outlet communicating with an annular channel having} discharge openings leading therefrom to the'liquid chamher, and a valve for controlling flow of liquid from the pump chambers into the liquid chamber consisting of a collarfitting about the drive shaft and slidable along same and plungers projecting from the collar through openings formed in the block and across the channel and the discharge openings transversely thereof to control flow of provide a liquid chamber in the casing, a drive shaft fixed to and extending outwardly from said block, a driven shaft passing through the side wall and rotatably mounted at the center ofthe block, said block having pump chambers therein,

rotary pumps in the pump chambershaving shafts extending into the liquid chamber, a gear carried by said driven shaft, gears carried by the pump shafts and meshing with the gear of the driven shaft, said pump chambers having an inlet and an outlet, the block being formed: with a circular channel with which outlets of the pump chambers communicate and with discharge pas.-

' sages leading from the channel to the liquidchamber, the block being also formed with longitudinally extending openings aligned with the-outlets of the pump chambers and with drain passages leading from the said longitudinally .extending openings intermediate the length=thereof, and a valve having a collar slidable along'the drive shaft and plungers extending from the col.-

lar and through, the longitudinally. extending openings in the block, said plungers passing through the circular channel and being movable into and out of the outlets and each being formed intermediate its length with a circumferential groove moved into and out of registry with .the

drain passage leading from the opening in the block in which the plunger fits when the plungers mi f d along the are shifted longitudinally into and out of a clos ing position. I

' '3. In a hydraulic transmission, a casing havin a liquid chamber therein and provided with circumferentially spaced, pump chambers at one side of the liquid chamber, a drive shaft fixed to said side of said casing whereby the casing turns with the drive shaft, a driven shaftrotatably mounted through the other side of the casing in alinement with the drive shaft, rotary pumps-in the pump chambers having shafts extending across the liquid chamber in spaced parallel relation to the driven shaft and geared to the driven shaft, each pump chamber having an inlet toward the periphery of the casing, there being-an annular outlet channel communicating with all of the pump chambers and discharge passages leading from the annular channel between cer-' tain of the pump chambers to the liquid chamber, a valve having a collar slidable along the drive shaft and plungers extending from the collar and slidably engaged in openings intersecting the annular channel at the discharge passages,- and means for shifting said collar along the drive shaft and gradually moving the plungers into 'and out of closing relation to the discharge openings.

4. In a hydraulic transmission, a casing having a liquid chamber therein and provided with circumferentially spaced pump chambers at one side of the liquid chamber, a drive shaft fixed to the said side of said casing whereby the casing turns with the drive shaft, a driven shaft rotatably mounted through the other side of the casing in alinement with the drive shaft, rotary pumps in the pump chambers having shafts extending into the liquid chamber and provided with gears meshing with a gear carried by the driven shaft,

each pump chamber having an inlet communieating with the liquid chamber and an outlet, there being a channel communicating with all of the outlets and discharge openings leading from the channel to the liquid chamber, and a valve having a collar shiftable longitudinally of ide wallto the drive shaft and having plungers passing able casing having a shaft rigid with one side and a second shaft rotatably engaged with its other side, said casing having a liquid chamber therein and pump chambers extending transversely of the liquid chambers and disposed about the shafts, rotary pumps in said pump chambers and having shafts extending into the liquid chamber, means for transmitting rotary motion from the second shaft to the pump shafts, said casing being formed with an annular channel concentric with the shafts and surrounded by the pump chambers, the pump chambers having inlets and outlets spaced from the inlets and communicating with said channel, there being discharge openings leading from said channel, and a valve having plungers slidable through the channel transversely thereof and formed with grooves moving into and out of registry with the discharge openings as the plungers are moved.

6. In a hydraulic transmission, a casing having a liquid chamber therein and provided with circumferentially spaced pump chambers at one side of the liquid chamber, a drive shaft fixed to said side of said casing whereby the casing turns with the drive shaft, a driven shaft rotatably mounted through the other side of the casing in alignment with the drive shaft, rotary pumps in the pump chambers having shafts extending into the liquid chamber and provided with gears meshing with a gear carried by the driven shaft, each pump chamber having an inlet communicating with the liquid chamber and an outlet, a channel communicating with all of the outlets and also communicating with the liquid chamber, and a. valve movable into and out of position for gradually cutting oif flow of liquid from said channel and thereby stopping rotation of the pump shafts to cause turning of the driven shaft with the easing and the drive shaft.

7. In a hydraulic transmission, a casing having a liquid chamber therein and provided with circumferentially spaced pump chambers at one side of the liquid chamber, a drive shaft fixed to said side of said casing whereby the casing turns with the drive shaft, a driven shaft rotatably mounted through the other side of the casing in alignment with the drive shaft, rotary pumps in the pump chambers having shafts extending into the liquid chamber and provided with gear meshing with a gear carried by the driven shaft, each pump chamber having an inlet and an outlet spaced from the inlet circumferentially of the pump chamber, the portion of the peripheral wall of each pump chamber between its inlet and its outlet being eccentric to the chamber and the rotary pump therein, said pumps having blades slidable radially thereof and urged outwardly for contact with the peripheral walls of the pump chambers and applying pressure to liquid as they move toward the outlets of the pump chambers, an annular channel communicating with the outlets of all the pump chambers and having discharge openings leading therefrom between certain of the outlets to the liquid chamber, a collar slidable along the drive shaft, and plungers extending from the collar and through the channel at the discharge openings and constituting valve members for gradually shutting off flow of liquid from the channel and the pump chambers as the collar is shifted along the drive shaft in one direction.

8. In a hydraulic transmission, a casing having a liquid chamber therein and provided with circumferentially spaced-chambers at one side of the liquid chamber, a drive shaft fixed to said side of said casing whereby the casing turns with the drive shaft, a driven shaft rotatably mounted through the other side of the casing in alignment with the drive shaft, rotary fluid brakes in the spaced chambers having shafts extending into the liquid chamber and provided with gears meshing with a gear carried by the driven shaft, each spaced chamber having an inlet and an outlet spaced from the inlet circumferentially of said chamber and communicating with the liquid chamber, the side wall of the casing having an extension about the driven shaft and an adaptor about the driven shaft rotatably engaged by the outer end of said extension, a portion of the said side wall of the casing forming a side wall of the extension and being formed with openings leading from the liquid chamber, a pipe for connecting said adaptor with a reservoir, the drive shaft being formed with a liquid passage having radiating branches leading to inlets of the pump chambers, a coupling surrounding the drive shaft at the inlet of its liquid passage, and a pipe extending from the coupling for connection with the reservoir.

9. In a hydraulic transmission, a casing having a liquid chamber therein and provided with circumferentially spaced chambers at one side of the liquldchamber, a driven shaft fixed to said side of said casing whereby the casing turns with the driven shaft, a drive shaft rotatably mounted through the other side of the casing in alignment with the driven shaft, rotary fiuld brakes in the spaced chambers having shafts extending into the liquid chamber and provided with gears meshing with a gear carried by the drive shaft, each spaced chamber having an inlet and an outlet spaced from the inlet circumferentially of said 'chamber and communicating with the liquid chamber, the side wall of the casing having an extension about the drive shaft and an adaptor about the drive shaft rotatably engaged by the outer end of said extension, the side wall of its extension being formed with openings leading from the liquid chamber, a pipe for connecting said adaptor with a reservoir, the driven shaft being formed with a liquid passage having radiating branches leading to inlets of the pump chambers, a coupling surrounding the driven shaft at the inlet of its liquid passage, and pipe extending from the coupling for connection with the reservoir.

10. In a hydraulic transmission, a casing having a liquid chamber therein and circumferentially spaced pump chambers at one side of the liquid chamber, a drive shaft fixed tosaid casing at a side thereof, a driven shaft rotatably mounted through the other side of the casing, bearings about said shafts rotatably mounting the shafts and permitting rotation of the casing-relative to the driven shaft, the drive shaft being formed with an inlet passage communicating with the pump chambers and the fluid chamber having an outlet extending through the bearing about the driven shaft, rotary pumps in the pump chambers having shafts extending into the liquid chamber, intermeshing gears carried by the pump shaftsand the driven shafts, means for controlling fiow of liquid through the pump chambers and thereby regulating rotation of the pumps and the speed at which the driven shaft is rotated and pipes for connecting the inlet and the outlet with opposite ends of a reservoir through which liquid is circulated during operation of the transmission.

11. In a hydraulic transmission, a casing having a liquid chamber therein and circumferentially spaced pump chambers at a side of the liquid chamber, a drive shaft extending from the said side of the casing and formed with an inlet communicating with the pump chambers, a neck extending from the opposite side of the casing, a driven shaft passing through said neck into the liquid chamber, rotary pumps in the pump chamber having shafts extending into the liquid chamber and geared to the driven shaft, stationary adaptors about the drive shaft and the driven shaft, the adaptors about the driven shaft rotatably engaging the neck and cooperating therewith to provide an outlet for the liquid chamber, pipes for connectingthe adaptors with an outside liquid reservoir and establishing a circulation of liquid through the casing and its chamber during operation of the transmission, and valve means for controlling flow of liquid and thereby regulating the speed at which the driven shaft is rotated by action of the pumps.

12. In a hydraulic transmission, a casing, a drive shaft extending from a side of the casing, a drive shaft entering the casing through the other side thereof, stationary adaptors rotatably supporting the shafts and the casing, rotary pumps in the casing connected with the driven shaft by gearing for rotating the driven shaft during rotation of the casing, and the drive shaft, one adaptor having an inlet communicating with the rotary pumps and the other adaptor having an outlet for escape of liquid from the casing, pipes for connecting the inlet and the outlet with an outside reservoir whereby a circulation of liquid may be established through the pumps and the casing, and valvemeans for controlling flow of liquid through the pumps and thereby regulating rotation of the pumps and the speed at which the driven shaft rotates.

13. In a hydraulic transmission, a casing, a drive shaft extending from a side of the casing, a driven shaft entering the casing through the other side thereof, said casing having a liquid chamber therein and circumferentially spaced pump chambers at a side of the chamber, rotary pumps in the pump chambers having shafts extending into the liquid chambers and carrying gears meshing with a gear upon the driven shaft,

' a stationary adaptor for the drive shaft having a liquid inlet communicating with a passage leading to the pump chambers, a stationary adaptor for the driven shaft and the casing having an outlet communicating with the liquid chamber, pipes for connecting the inlet and the outlet with a liquid reservoir, and valve means for controlling flow of liquid through the pump chambers.

14. In a hydraulic transmission, a casing, a drive shaft extending from a side of the casing, a driven shaft entering the casing through the other side thereof, said casing having a liquid chamber therein and circumferentially spaced pump chambers at a side thereof, rotary pumps in the pump chambers having shafts extending into the liquid chamber and carrying gears meshing with a gear upon the driven shaft, the pump chambers each having an inlet and an outlet spaced from the inlet circumferentially of the pump chamber and communicating with a circular 'passage'withinthe casing and communieating with discharge'passages formed in the casing parallel with'the' shafts and communicating with the liquid chambera'the said discharge passages each having communication with the circular passage .at apoint between two of said outlets for, and valve .me'ans'for controlling flow of liquid from the pump chambers havingplungers slidable in the discharge passage to adjusted posions.

15. In a hydraulic transmission, a casing, a drive shaft extending from a side of the casing, a driven shaft entering the casing through the other side thereof, sa'id'casing having a liquid chamber therein and circumferentially spaced pump chambers at a side thereof, rotary pumps in the pump chambers-and carrying gears meshing with a gear upon the driven shaft, the pump chambers each having an inlet and an outlet spaced from the inlet circumferentially of the pump chamber and communicating with a circular passage concentric with the casing and the shafts and communicating with discharge passages, the rotary pumps each having a body circular in cross section and carrying radially extending blades spaced from each other circumferentially of the body, the walls of the pump chambers having an arc radial to axes of the rotor for a portion between the inlet and the outlet covering an arc of greater length than the angular distance between two blades of a pump, and valve means for controlling flow of liquid from the pump chambers through the discharge passages.

16. In a hydraulic transmission, a casing having side walls and a peripheral wall, a drive shaft extending from a side of the casing, a driven shaft entering the casing through the other side thereof, said casing having a liquid chamber therein and circumferentially spaced pump chambers at a side thereof, rotary pumps in the pump chambers having shafts extending intov the liquid chamber and carry gears meshing with a gear upon the driven shaft, the pump chambers each having an inlet extending through one side of wall of said casing and an outlet spaced from the inlet circumferentially of the pump chamber and communicating with a circular passage with the casing and communicating with discharge passages formed in the casing parallel with the shafts and communicating with the liquid chambers, the said discharge passages each having communication with the circular passage, and valve means for controlling flow of liquid from the pump chambers including plungers slidable longitudinally in the discharge passage to opened and closed positions.

17. In a hydraulic transmission, a casing, a drive shaft extending from a side of the casing, a driven shaft entering the casing through the other side thereof, said casing having a liquid chamber therein and circumferentially spaced pump chambers at a side thereof, rotary pumps in the pump chambers having shafts extending into the liquid chamber and carrying gears meshing with a gear upon the driven shaft, the pump chambers each having an inlet and an outlet spaced from the inlet circumferentially of the pump chamber and communicating with a circular passage disposed concentric with the casing and the shafts and communicating with discharge passages, the rotary pumps each having a shaft and a body circular in cross section and formed with radially extending pockets spaced from each other circumierentially oi the body, blades in said pockets urged outwardly and bearing against the annular walls of the pump chambers, the shafts of the pumps being formed with longitudinal passages and with branch passages communicating with the pockets and the liquid chamber to prevent formation of fluid cushions under the blades, and valve means for controlling flow of liquid from the pump chambers through the discharge passages.

VERNON E.

REFERENCES crrnn 5 UNITED STATES PATENTS Number Name Date 1,956,893 Carter May 1, 1934 2,146,717 Berger Feb. 14, 1939 10 2,178,804 Murphy Nov. 7, 1939 2,218,896 Schultz Oct. 22, 1940 FOREIGN PATENTS Number Country Date Great Britain Aug. 2, 1928